\documentclass{article}
\usepackage{amssymb,amsmath,amscd,concmath}
\pagestyle{empty}
\begin{document}
\begin{equation*} \hat{\textbf{x}}_{k|k-1} = \textbf{F} \hat{\textbf{x}}_{k-1|k-1} \end{equation*}
\end{document}
